What to do in your garden this month

This monthly guide is geared to London gardens and their unique conditions. Compiled by the RHS Wisley Plant Centre team

Sunday 1 August 2010 23:00 BST

Prune out the flowered stems of rambling roses when they've finished to encourage new growth for next year's garden

Must do in your garden this month

* When rambling roses have finished, prune out the flowered stems to encourage new young shoots to develop for next year’s display.

* Prune your wisteria to reduce the side stems back to about 20cm from the main framework - this helps to ensure that the plant will produce flowering buds for next spring.

* With the continuing hot weather don’t be tempted to get hoses out and just spray everything including the ground. Surface watering only encourages plant roots to come to the surface. This will make them more vulnerable to drying out. Localised watering, delivered to the base of your plants, is much more effective. To help keep flowering plants going, you can use washing-up water around established plants. Do not use water from dishwashers as this water contains harsher cleaning products and could damage plants.

* Where possible try and mulch around plants to help contain any water in the soil. A layer of gravel or bark chips in tubs and containers not only looks attractive but also slows water evaporation. Also, standing tubs in saucers keeps the soil more moist.

* If you are going away ask friends or neighbours to water the plants for you. Take all moveable tubs and baskets to the shadiest part of the garden, but still accessible to a water supply, and group them together. This makes it easier for the person watering and also makes a micro-climate that is more humid which will keep the plants happier.

* In the greenhouse keep paths and benches damped down to raise humidity. This will help plants and also keep red spider mite in check, as these pests thrive in hot, dry conditions.

Keep picking runner beans to keep them cropping

* Make sure you keep picking runner beans to keep them cropping. The flowers will stop if you leave any on the vine that start to mature.

* August is the time that vine weevil hatch out and now is the best time to treat pots and susceptible plants with nematodes or Provado to stop this pest.

* With the continuing hot weather, powdery mildew is a problem. Remove any badly affected leaves and then spray with a systemic fungicide, such as “Systhane fungus fighter”.

* Continue to liquid feed all flowering tubs and baskets, dead head regularly and cut back bedding plants, such as lobelia, to produce a second flush of flowers.

Nice to do in your garden this month

* Cut out the fruited canes of early raspberries to encourage new canes to fruit next year.

* Sow a few rows of salad crops in containers or small areas in the garden to give you a crop in September/October. Radishes, spinach and lambs lettuce will all take a light frost and still be viable.

* Hoe around existing plants to remove annual weeds that use up precious water

* Look out for autumn-flowering bulbs arriving in garden centres. Saffron crocus, colchicums and various species should be planted as soon as you see them to give them a chance to root properly for a much longer flowering period.

* Turn your compost heap at the end of the month to let it settle down for the autumn and you won’t then disturb any animals who make their home in there during the winter months.

Continue to liquid feed all container plants throughout August

* Plant up some winter hanging baskets with pansies and evergreen foliage and underplant with dwarf bulbs as they become available. Hang in a shady spot to allow everything to root and establish before the colder weather and you will have a much better show.

* In your cold frame or greenhouse now, on a good day, is the time to take everything out and clean or spray the whole framework with a plant-friendly disinfectant, such as Citrox. Get into all the crevices to get at pests and spores that are lurking there.

* After you have finished cleaning check any plants for pests and diseases before returning them and spray or remove any “passengers”.

* Start some potatoes in containers to produce new potatoes at Christmas. Tubers should be available in the garden centres.

* Finally, sit back and relax... August is for reflecting on your gardening triumphs and disasters. Use your journal to record them so you don’t forget when you set out again in the spring.

All images provided courtesy of the Royal Horticultural Society. Visit the online print shop at www.rhsprints.co.uk.